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Solution: Knowing m(h)=, m(c)=, then m(o)=

Then n(c) n(h) n(o)=, then the experimental formula is ch2o

Therefore, the molecular formula can be set to (CH2O)N, then there is 30N=90, and the solution obtains: N=3, so the molecular formula is C3H6O3

Organic matter.

Contains a coefficient of 6

Contains a coefficient of 3

The rest is o (90-6-36) 16=3

Then the formula is c3h6o3

The molecular formula of organic matter is C3H6O3

The physical mass of the compound

The material quality of the water

The mass of carbon dioxide

So the compound: water:CO2 1 to 3 to 3

It can be judged that the composition of the compound may be C3H6OX

12*3+（1*6）+(16*x)=90

Calculate that x=3 and finally get c3h6o3

In pure oxygen, the mass of the water knows that all the h in the water comes from the compounds.

The C in CO2 comes entirely from the compound, and the rest is oxygen, and finally calculate the ratio by yourself and match it with the relative molecular mass given.

It is better to teach a man to fish than to teach him to fish!!

A good way to learn chemistry is to grasp the essence of reactions in chemistry! It's all out of the way!

You can calculate the mass of sodium carbonate by equation and then subtract the calculated data. The first substance to react is NaOH, and the amount of strong acid consumed remains the same. Come on, this kind of topic is not difficult.

Analysis: Combined.

Topic. Information can be known that boric acid.

Molecule. It's because.

Central atom. There are only six around boron.

Electron. When dissolved.

to water. when only combined with water. Ionization. Target.

Hydroxide ions.

. Oxygen atoms.

Above. of electrons.

And a stable structure that reaches eight electrons. Thus the ionization balance of the water is disrupted, the ionization of the water is promoted, and the remainder is left.

Hydrogen ions. And make. Solution. Submit.

Acidity. And, a boric acid molecule binds only one hydroxide ion of water to produce a hydrogen ion. So, boric acid is.

Monoacid. Analyze the options, only C is correct.

Answer: c

Select C for this question

H2SO4 contains H mass 2 98

Because it is a reaction, the oxygen element is conserved

h2o~~~2h

So the mass of the generated water is grams, and the mass of the oxygen element is .

Satisfied, if you have any doubts, please ask! ~

There is a reaction equation to know that the oxygen elements in the original mixture are transferred to the water in the reactants, and all the hydrogen in the mixture is transferred to the water, that is to say, what is the mass of the oxygen elements in the original mixture, only the mass of the water generated by the reaction minus the mass of hydrogen in the sulfuric acid is required.

c. Complete reaction, that is, all the hydrogen elements in the sulfuric acid produce water.

One part H2SO4 corresponds to one part H2O The oxygen element in the water comes from the oxygen element in the mixture, and the water gram is obtained from the gram of sulfuric acid, then the oxygen element gram.

Choose C, because a complete reaction of one iron oxide requires 3 parts of sulfuric acid (assuming that the sulfuric acid is 3x mol), and a complete reaction of one copper oxide requires 1 part of sulfuric acid (assuming y mol), then 3x+y=, then the amount of the corresponding iron oxide and the oxygen element in the copper oxide is , and the mass is.

Hydrogen. Helium.

Lithium. Beryllium. Boron. Carbon.

Nitrogen. Oxygen. Fluorine. Neon.

Sodium. Magnesium. Aluminium. Silicon.

Phosphorus. Sulfur. Chlorine. Argon.

Potassium. Calcium. Scandium. Titanium.

Vanadium. Chromium. Manganese. Iron.

Cobalt. Nickel. Copper. Zinc.

Gallium. Germanium. Arsenic. Selenium.

Bromine. Krypton.

Reaction equation: 2NaHCO3 = Na2CO3 + H2O + CO2 Water and carbon dioxide are lost during heating, so the remaining substance is sodium carbonate.

Because 2molNaHCO3 is heated to produce 1molNa2CO3, n(Na2CO3) = 1 2N(NaHCO3) = 1 2* (for multiplication, for division).

M(Na2CO3)=N(Na2CO3)*M(Na2CO3)=

2NaHCO3 = (heating) Na2CO3 + CO3 + H2O Heating to no gas generation indicates that it has been completely decomposed, the original amount of sodium bicarbonate is twice the amount of sodium bicarbonate before and after the reaction = the mass of sodium carbonate after the reaction is 106 * grams.

The addition of zinc chloride is one way to go.

In the concentrated solution of zinc chloride, it has significant acidity due to the formation of compound acid --- hydroxydichlorozinc acid, which can dissolve metal oxides

zncl2+h2o===h[zncl2（oh）] feo+2h[zncl2(oh)]===fe[zncl2(oh)]2+h2o

The removal of oxides from the metal surface with a concentrated solution of zinc chloride when welding metals is based on this property. The 'wrought water' used in welding metals is a concentrated solution of zinc chloride. It does not damage the metal surface during welding, and after the heat of water evaporates, the molten salt covers the metal surface, so that it no longer oxidizes.

The addition of sulfuric acid increases the concentration of hydrogen ions.

Let's take advantage of the principle of the galvanic battery.

Add a little copper sulphate.

Construct a Fe-HCL-Cu galvanic cell.

It should be ok.